Screw connections having similar rings are known from DE-B 1 167 608, DE-B 1 175 639, GB 1 117 987 A and U.S. Pat. No. 2,406,488, in all of which screw connections, however, the stop for the stop part is situated on the end side of the cutting ring.
For example, DE-B 1 167 608 describes a threaded attachment joint for tubes comprising an attachment piece which has an end face which runs perpendicular to the tube axis and a similarly-running annular face for supporting the tube end. In addition, the threaded joint comprises a sleeve nut which encloses the tube end and can be screwed onto the attachment piece, and a hardened sealing ring, which is arranged on the tube end. As the sleeve nut is tightened, the hardened sealing ring bites with a radially inward aligned cutting edge, which is arranged in the region of its rear end, into the tube outer face. The hardened sealing ring also bites with an end-side annular cutting edge, which can also be regarded as a stop, into the end face of the attachment piece, with that part of the sealing ring being guided, with little play, at the outside by the wall of the cylindrical bore adjoining the end face, and at the inside by the outer face of the tube end.
DE-B 1 175 639 describes a method for producing a sealing ring for tube connections. The sealing ring is between the receiving cone of an attachment piece and a press-in piece, which interacts with said attachment piece, and bites with a hard cutting edge into the outer casing of the tube. This outer casing is to be attached as said press-in piece is axially displaced, with the front part of the sealing ring being altered from a cylindrical shape into a conical shape by means of rotating rollers until a lug is formed, which projects beyond the outer edge of the front part.
GB 1 117 987 A describes a tube coupling with which, as a tube is attached, the tube end can be expanded. Serving this purpose is a ring, referred to as a “tube-flaring sleeve”, which fixedly holds the tube which is to be expanded by means of a radially inwardly aligned cutting edge when, during attachment, the end of said tube is pressed against a conical, centrally arranged expanding body, referred to as a “flaring member”. At the end side, the expanded tube portion comes into contact with a radially outer conical face of a mating bore. The ring, at the end side which faces towards the expanding body and the mating bore, has a radial cutting edge and axially outwardly and inwardly aligned inclined faces which have different bevel angles and are matched to the conical faces of the expanding body and the mating bore.
A tube connection having a cutting ring is also recited in U.S. Pat. No. 2,406,488. The cutting ring has a flange which points obliquely radially inward and, during attachment, is bent back, by an attachment piece which bears against it, from an original inclined position into a position aligned approximately perpendicular to the longitudinal axis of the connection, and thereby cuts into the casing of the tube which is to be connected. The cutting ring also has on an end face, an axially aligned annular rib which, during attachment, comes into contact as a stop against the attachment piece and thereby stops the bending movement of the flange.
A metallic cutting ring which corresponds to the type specified in the Background Section is known from DE 33 41 726 A1. Said document describes a screw connection for sealingly connecting a tube to a tube connecting part or screw-in part, composed of a body. The body has a bore which narrows conically in a continuous fashion from an end face to the interior of the body. A nut, which can be screwed onto the body, has a bore, which narrows conically away from the body. A intermediate ring is provided with its end facing the body with a plurality of radially inwardly aligned cutting edges and is held in a clamped fashion between the conical bore in the body and the conical bore in the nut. This is intended to achieve the object of providing, with the intermediate ring, a cutting ring which, while having a high degree of axial strength, has a low degree of deformation work in the radial direction. This is achieved in that axially aligned ribs are arranged so as to be uniformly distributed on the periphery of a solid region of the cutting ring. It is possible by means of a targeted formation of the ribs to provide the cutting ring with an elastic behavior, which is matched to the respective requirements. In order to additionally provide that assembly process is complete, the nut-side conical stop faces of the solid region and the rib region are offset against one another in a defined way. In the known cutting ring, an annular bead is provided on the nut-side end with the ribs being situated on the outside of said annular bead. Also, a tube abutment section is formed in the region of said annular bead. Where an inner lateral surface of said region encloses, in a positively engaging manner, the outer lateral surface of the tube, which is to be connected.
The tube abutment section is adjoined in the axial direction towards the body by a cutting section, which has a stop that points radially outward from the periphery of the cutting ring and runs transversely with respect to the cutting ring longitudinal axis for the attachment part. In one embodiment, a stop face of the stop runs perpendicularly to the longitudinal axis of the ring, and in a further embodiment, obliquely with respect to the longitudinal axis of the ring, and in each case merges into said ribs, which are situated further radially outward. The stop face acts as a tightening limiter as the nut is tightened. That is to say, when the stop face comes into firm contact with the attachment part, the tightening torque increases abruptly, thereby signaling the end of the assembly process.
In contrast to DE-B 1 167 608, the cutting ring of DE 33 41 726 A1, permits a limitation of tightening during assembly, and the arrangement of an additional sealing edge in the front ring region.